This has been covered ‘a lot’.
There are two Tenor ‘instruments’ you can choose in Setup: one transposes at the octave; the other is ‘at pitch’. Use the second if you want to use clefs that affect the octave pitch, or if you want to use other clefs for that voice.
See my post here for details about using the ‘at pitch’ Tenor.
Using this will also work well for XML export. MIDI export should work out correctly either way.
If you’re asking how do ‘real’ tenors cope wit a C4 clef, then it depends on the tenor.